Albert Barnes Commentary Jeremiah 6:23

"They lay hold on bow and spear; they are cruel, and have no mercy; their voice roareth like the sea, and they ride upon horses, every one set in array, as a man to the battle, against thee, O daughter of Zion." — Jeremiah 6:23 (ASV)

Spear - Properly, a javelin for hurling at the enemy (see 1 Samuel 17:6 note): an ordinary weapon of the Babylonians.

Cruel - ruthless, inhuman. In the Assyrian monuments warriors put the vanquished to death; rows of impaled victims hang around the walls of the besieged towns; and men collect in heaps hands cut from the vanquished.

Horses, set in array - A period should be put after horses. It - the whole army, and not the cavalry only - is set in array.

As men for war against thee - Rather, as a warrior for battle against thee.